How Belief Works

WHY DO WE BELIEVE WHAT WE BELIEVE?

How Belief Works is an ongoing series of articles on the psychology of belief that's best read in sequence.

It might seem obvious why we believe what we believe. We believe something because we've assessed that it's true – however brief, faulty, emotional or credulous our assessment was. But this understanding of how beliefs form is fatally logically flawed. To see why, consider first the difference between claim X and the claim X is true.

Claim X versus the claim X is true

Compare these two sentences:

2 can seem to be just a different wording of 1. That is, 1 and 2 can seem to be making the same claim.

But whereas 1 is making a claim about simply the current weather, 2 is making a claim about a claim about the current weather.

Diagram illustrating the difference between what 1 and 2 are about

So 1 and 2 are actually making different claims that merely imply each other. That is, if it’s raining then the claim It’s raining is true, and vice versa.

If two sentences are different wordings of the same claim, then, by definition, their content is the same. And if the content of two sentences is the same, then, by definition, neither sentence will refer to something that the other doesn’t refer to. But whereas 2 refers to the claim It’s raining, 1 doesn’t. That is, 1 makes, rather than refers to, the claim It's raining. Also, 2, unlike 1, refers to the concept of truth, and thereby also, unlike 1, to the relationship between the claim It’s raining and reality.

2 can be slightly reworded as follows:

The claim It’s raining is a true claim.

And it should now be even more apparent that 1 and 2 are making different claims that merely imply each other. That is, if it’s raining then the claim It’s raining is a true claim, and vice versa.

So 2 is merely implicitly making the claim that 1 is making.

2 can seem to be just a different wording of 1 because the claim made by 1 follows so obviously from the claim made by 2 that we can fail to notice the very basic logical step separating these claims.

The following two sentences are two more alternative wordings of 2:

It’s true that it’s raining.

The truth is that it’s raining.

Given that they don't use the wording 'the claim It's raining' they might seem to be referring to simply the current weather, rather than to a claim about the current weather, and so to actually be different wordings of 1.

However, unlike 1, they refer to the concept of truth. And this concept concerns a claim – specifically, a claim matching reality. The term true belief can either mean belief of a true claim – which is a belief as in believing something – or a true claim that’s believed – which is a belief as in something believed.

So when we say ‘It’s true that…’ or ‘The truth is that…’ we’re saying that the claim made by the subsequent words is a true claim. Therefore the above two sentences are actually both referring to the claim It’s raining. That is, they’re both asserting that the claim It’s raining is a true claim, as 2 does, even though they don’t explicitly refer to the claim It’s raining as a claim, as 2 does.

The difference between the claims made by 1 and 2 of course applies to any claim, X, and the claim X is true. So claim X isn’t in itself the claim that X is true, and vice versa. Instead, each claim merely implies the other.

Now consider our belief of claim X and of the claim X is true.

Belief X versus the belief X is true

Belief of one claim is by definition a different belief from belief of a different claim. So, given that the claims made by sentences 1 and 2 are different claims that merely imply each other, our belief of them are by definition different beliefs that merely imply each other. That is, if we believe that it’s raining then we’d conclude, and thereby believe, that the claim It’s raining is a true claim. And, conversely, if we believe that the claim It’s raining is a true claim then we also believe that it’s raining.

But our belief of these two claims can seem to be the same belief because, again, the claims follow so obviously from each other that we can fail to notice the very basic logical step separating them.

The difference between our belief of these two claims of course applies to our belief of any claim, X, and the claim X is true. So believing X isn’t in itself believing that X is true, and vice versa. Instead, believing X merely implies that we’d conclude, and thereby believe, that X is true, and believing that X is true merely implies that we believe X.

The true relationship between assessing that claim X is true and believing X

The difference between believing claim X and believing that X is true implies a fatal logical flaw in the idea that we believe X because we’ve assessed that X is true. If believing X was dependent on us believing that X is true, then believing that X is true would in turn be dependent on us believing that the claim X is true is true, and so on – which implies an infinite chain of belief formation. So belief formation would be impossible.

And there’s actually a second fatal logical flaw in this theory of belief formation – one which reveals the true relationship between assessing that X is true and believing X.

By definition, a claim is a true claim if, and only if, it matches reality. So the only way to assess whether a claim is a true claim is to assess whether it matches reality. And the only way to assess whether a claim matches reality is to compare it with reality. But when we compare a claim with reality we can only ever compare it with what we believe about the relevant aspect of reality at the moment of the comparison, even when the comparison uses the current content of our senses.

So our assessment that the claim It’s raining is a true claim must be based on our belief that it’s raining. That is, this assessment must be preceded by our belief that it’s raining. So our belief that it’s raining can’t ever be due to us assessing that the claim It’s raining is a true claim.

And this logic of course applies to the formation of any belief: our belief of claim X can’t ever be due to us assessing that X is true, because that assessment is always based on, and so preceded by, our belief of X.

Although, the process of assessing the truth of X can lead to the formation of our belief of X, because this belief may only form during that process, the moment before we conclude that X is true.

It might be thought that our assessment that X is true is by definition an instance of believing something because we’ve assessed that it’s true. But this belief involves the claim X is true, and yet is due to our assessment that X, not X is true, is true.

Potential objections

Objection 1

It might be objected that even if we accept the above analysis there’s still one scenario in which we believe claim X because we’ve assessed that X is true.

If we read or hear X, and we neither believed or disbelieved X immediately before doing so, and we completely trust X’s source on the subject of X, then we can assess that X is a true claim based on that trust, and this assessment will then immediately lead us to conclude X. This sequence of events doesn’t imply the infinite chain of belief formation that I referred to earlier, given that our belief that X is true is based on our trust of X’s source and so isn’t dependent on us believing that the claim X is true is true.

Of course, not all of our beliefs follow from us reading or hearing the believed claim when we completely trust the claim’s source on the subject of the claim. Many of our beliefs follow instead from our generation of the believed claim via our reasoning. In the case of such beliefs that are about our surroundings or body, our reasoning is aided by our senses.

Indeed, in the above sequence of events our belief that X is true results from our generation of the claim X is true via our reasoning, based on our trust of X’s source, rather than following from us reading or hearing the claim X is true.

So the aim of this objection isn’t to show that our belief of X is always due to us assessing that X is true. Indeed, if it was, the objection wouldn’t provide a solution to the resulting problem of the infinite chain of belief formation.

But the objection doesn’t even succeed in its limited aim of showing that our belief of X is sometimes due to us assessing that X is true, because it has two flaws.

First, in the above sequence of events our conclusion that X is a true claim actually isn’t an assessment that X is a true claim.

Again, by definition, a claim is a true claim if, and only if, it matches reality. So the only way to genuinely assess whether a claim is a true claim is to assess whether it matches reality. And the only way to genuinely assess whether a claim matches reality is to compare it with reality – that is, compare it with what we believe about the relevant aspect of reality at the moment of the comparison, even if that belief is based on the current content of our senses.

So if our conclusion that a claim is a true claim is based on simply a consideration of its source, and therefore not on a comparison of it with reality, then it’s based on an assessment of not its truth but that source. Therefore in the above sequence of events our belief of X is actually based on us concluding, but not assessing, that X is true.

The second flaw in this objection is that our complete trust of X’s source on the subject of X actually leads directly to us concluding X, rather than via concluding that X is a true claim.

That is, although that complete trust means, by definition, that we believe that all claims produced by the source on the subject of X can be believed to be true claims, this in turn means that we also believe that all such claims can be believed. So upon reading or hearing X we can conclude X directly rather than via concluding that X is a true claim. And given that the former mental route to concluding X is shorter than the latter, we conclude X via the former route before we’ve had a chance to do so via the latter.

Objection 2

It might also be objected that if our assessment that claim X is true was based on our belief of X, rather than the reverse, then our belief of X would lead us to always assess that X is true and that any contrary claim is false, and so we’d never change our belief, and yet we do change our beliefs.

But this objection wrongly assumes that if we believe X then changing this belief is dependent on us assessing that X is a false claim and that a contrary claim is a true claim. Just as our belief of X can’t be due to our assessment that X is a true claim, because the reverse is true, so the subsequent formation of a contrary belief, and thus the end of our belief of X, can’t be due to us assessing that the contrary claim is a true claim and that X is a false claim, because the reverse will be true.

Also, as I said earlier, the process of assessing the truth of X can lead to the formation of our belief of X, because this belief may only form during that process. Likewise, if we believe X and then assess the truth of both X and a contrary claim, we can change to believing the contrary claim during this process, and then assess that the contrary claim is a true claim and that X is a false claim. So believing X before assessing the truth of both X and a contrary claim doesn’t even mean that we’ll necessarily assess that X is a true claim and that the contrary claim is therefore false.

The origin and persistence of this false theory of belief formation

The origin and persistence of the idea that we believe claim X because we’ve assessed that X is true is likely due to the combination of the following factors:

So why do we believe what we believe?

There’s actually a third fatal logical flaw in the idea that we believe claim X because we’ve assessed that X is true.

We obviously can only begin to assess the truth of a claim after it has entered our mind, whether it does so upon us hearing it, reading it, recalling it, or generating it with our reasoning or imagination. But the entrance of a claim into our mind via our reasoning is a conclusion, which is by definition a belief. So we believe such a claim before we’ve had a chance to even begin to assess its truth.

The fact that a conclusion is by definition a belief can also seem to provide the answer to the question of why we believe what we believe: we believe claim X because we’ve concluded X. That is, we believe X because this claim was the product of our reasoning – however brief, faulty, emotional or credulous our reasoning was. Again, when we read or hear X we can then conclude X based on simply our complete trust of X’s source on the subject of X.

It might be thought that the formation of a belief about our surroundings or body via sensory perception doesn't require reasoning. For example, it might be thought that to see rain is in itself to believe that it's raining.

But given that the formation of any belief involves thinking a claim, the formation of a belief via sensory perception involves the generation of a claim about the physical world, and us thinking that claim, whereas the output of a perceptual process is simply a perceptual experience of the physical world. For example, the formation, via visual perception, of the belief that it's raining involves the generation of the claim It's raining, and us thinking 'It's raining', whereas the output of the visual process is simply our visual experience of rain.

When we form belief X about our surroundings or body via sensory perception claim X is generated by our reasoning, based on our perceptual experience, with our thinking X being the output of that reasoning. But such reasoning is often so basic and therefore brief that the resulting belief can seem to be a direct product of the perceptual process.

So even the formation of beliefs about our surroundings or body via sensory perception requires at least some reasoning.

The theory that we believe claim X because we've concluded X can seem true by definition and therefore irrefutable. But so can the theory that we believe X because we’ve assessed that X is true. And, incredibly, even the former is fatally logically flawed – as I'll show in the next article.

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Article history

This article was first published 10 January 2023. Past versions are available in the Internet Archive here.